1. Field of the Invention
The present invention relates to a digital fuzzy apparatus for performing fuzzy inference and, more particularly, to a digital fuzzy apparatus in which the circuit sizes of a maximum value operation unit and a center of gravity determining unit are reduced.
2. Description of the Related Art
The fuzzy theory was proposed by Prof. L. A. Zadeh, University of California, in 1965, as is well known, and a possibility of practical applications of the fuzzy theory was proposed by Prof. E. H. Mamdani, London University, in 1974. Various fuzzy inferential means have been proposed since then. Typical examples are as follows.
U.S. Pat. No. 4,852,007 (corresponding to Published Unexamined Japanese Patent Application No. 58-192407) describes a rolling stock operation control technique for reducing a notch variation count in accordance with a software inference. U.S. Pat. No. 4,716,540 (corresponding to Published Japanese Patent Application No. 61-20428) describes an analog fuzzy circuit realized by a current circuit.
Nikkei Electronics, No. 457, Oct. 3, 1988 describes a system employing a memory scheme practiced in Hohsei University or the University of North Carolina, and a fuzzy controller processor for writing inference data in an instruction memory, as proposed by Togai Infralogic Corp.
The conventional techniques described above, however, have the following drawbacks. More specifically, a fuzzy inferential system utilizing software can be realized by the state-of-art personal computers and microcomputers, but their inferential speeds are very low. In an analog fuzzy inferential system utilizing a current circuit, an interface is required when the system is used as an accessory to a digital computer. A fuzzy inferential system utilizing a memory scheme or a special-purpose processor requires large-scale development tools. In addition, since a memory is used, a system clock is also required. A high-speed clock is required to perform a high-speed inference. For this reason, such a system becomes a noise source when it is used near an analog circuit or the like.
In order to cope with the above situation, the present applicant proposes a high-speed, versatile digital fuzzy circuit in Japanese Patent Application No. 63-278797.
When the digital fuzzy circuit is to be formed into an IC (Integrated Circuit), it is important to determine how to simply design the circuit. In this respect, the digital fuzzy circuit disclosed in Japanese Patent Application No. 63-278797 has a complicated circuit arrangement and has much room left for a simpler circuit.